NDSU Extension - Ramsey County


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October 3, 2011 Agriculture Column


Driving around the county one cannot help but notice that harvest is progressing very well.  There is still much to be harvested but we could not have had better weather and sounds like we should have another 4-5 days of beautiful weather.  The article I added to the column today brings some very good points but the most important point is the timing of the fall application.  The timeline as suggested in the article below is right on but the soil temperatures have not met the 50 degree mark in the early morning.  Turf soil temperatures are 55 degrees at the Crary NDawn station taken on October 2.  I do not have a accurate reading at the 4 inch level but I would guess that we are still a week away or more for optimum placement of Nitrogen.  The best thing to do is to check your fields for soil temperatures.  Dave Franzen is very opinionated about an application of N to early.  He would tell you that if you want to throw your money away that you would be better served giving it to him.  Remember that Urea needs to be put on later.  Read below.

I have heard several growers exclaim that they will never fall apply nitrogen again. Although fall-applied fields often suffered more loss than spring-applied fields, it is not always the case.

Growers that applied late in the fall when our recommendations would suggest it was safer are more satisfied with their results than those that were early. For those who cannot recall our recommendations for fall nitrogen timing, here they are again.

  1. Do not fall apply N on soils that typically flood in the spring or to soils with sandy loam or coarser textures.
  2. Do not even think about applying anhydrous ammonia until October 1.
  3. After October 1, check the soil temperature measured at 4 inch depth from 6-8AM. When it hits 50 F, it is practical to apply anhydrous ammonia (but not urea!)
  4. A week after the date for anhydrous ammonia, growers can start applying banded urea.
  5. 2 weeks after the date for anhydrous ammonia, growers can start broadcast-incorporating urea.

This past season, the date the soil temperature dropped to 50 F was about October 15. That means that banded urea application should not have begun until October 22 and broadcast urea until October 29.

I know that a great deal of fall N was applied before these dates. I know that I traveled to Bismarck for a meeting about September 20 and there was a grower applying anhydrous ammonia to a field near Jamestown. I also saw urea applicators in the field about the same time in the Valley. This was a very bad plan.

                There is nothing wrong with well-timed fall N application in North Dakota. In years of dry weather, it didn’t matter when nitrogen was applied. If the last 18 years of wetness is an indication of the beginning of a trend, I think that this winter and spring will also be wet and we will be set up for losses for N that was applied too early. Agronomy does not always mesh with convenience. Although many growers have a ‘harvest gap’ in September after small grain harvest and before soybeans/corn/sunflower, it is not the time to fall apply N. P and K can be applied during this time, but not N. Too many bad things can happen to early applied N if it is applied too early with too much fall ahead of it.

                A nitrification inhibitor should be used not to move the date of application earlier, but to protect the N-applied at a safer date from unanticipated losses from early spring wetness. N-Serve™ can be applied with anhydrous ammonia to protect N from losses due to nitrification in the fall/spring. Instinct™ is an encapsulated form of nitrapyrin (active ingredient in N-Serve), and the label I have currently lists it as a spring additive with urea or UAN. Check with your Dow-Agro Sciences rep to see if it is labeled for fall application with urea. In the spring, products with the additive DCD (examples are Super-U™ by Agrotain, Int., or Guardian™ by Conklin) will also slow nitrification. One product that is sold as a nitrification inhibitor, but does not function like one is Nutrisphere™. It is neither a nitrification inhibitor nor a urease inhibitor and should not be used as one.

Dave Franzen - Extension Soil Specialist


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